Harold Katz bit into a raw onion and watched the numbers shoot up on his Halimeter.

The box, which looks like a large clock radio, measures bad breath. “It went up to 2,000,” Katz observed.

Bad breath doesn’t get any worse than this.

A reading of zero to 100 means your mouth smells okay, explained the Los Angeles dentist, in town to promote his line of breath-freshening products.

Anything over 200 can be grounds for marriage breakdown, job loss or even suicide.

Suicide?

That’s right.

Since he gave up his regular practice 12 years ago to wage full-time war on halitosis, Katz has seen its ravages.

He has treated patients who tried to slit their wrists, couples who sleep with a pillow between them, employees forced to work from home and lovelorn Romeos who can’t get a date – all because of jungle mouth.

One patient had her sweat glands removed and several had teeth pulled in unsuccessful attempts to tame the problem.

Katz has developed a mouthwash, toothpaste and breath spray, available in drugstores, under the brand name Thera Breath. He even sells clean-breath products for dogs and cats.

One person in three has bad breath, and most adults wake up with it in the morning.

And most of the things we use to fight it – mouthwash, toothpaste, breath mints and gum – don’t work, said Katz.

That’s because most contain ingredients like alcohol that cause a dry mouth – the No. 1 cause of halitosis, Katz explained. “If your tongue is pink and glistening, your breath is probably okay.”

A white coating on your tongue is a sign your mouth is overproducing anaerobic sulfur-producing bacteria that cause bad breath.

Sugar in gums and mints feed those bacteria.

Drinking six to eight glasses of water a day is the best way to cure bad breath. Foods that freshen breath include celery, carrots, apples and watermelon.

Katz also recommends taking vitamin C, D and zinc.

Spending five minutes a day in the sun is an even better way to get your vitamin D, he added.

Coffee causes dehydration and sours your breath, said Katz, who downs six to eight cups of java every day. “I always have a chaser of water.”

It’s a myth that bad breath comes from food digesting in your stomach. However, halitosis does plague lactose-intolerant people who eat dairy products. The odour-causing bacteria that break down proteins are working overtime in their mouths and throats.

It’s no surprise that cigarettes and liquor make your breath stink. The reason is that dry the mouth.

Katz started researching halitosis when his 13-year-old daughter came home in tears because friends were complaining about her breath. “She said, ‘All my friends keep offering me mints and gum.’ “

She had good oral hygiene and still has no cavities at age 28. The culprit was a rough tongue and large tonsils, combined with a dry mouth from doing sports. “That combination became a breeding ground for bacteria.”

Katz won’t divulge the names of celebrities he has treated for halitosis, but he does say that singers often have the problem because their mouths get dry.

One patient found out about her bad breath the hard way.

“She was belting out a song and the people in the front row got up and left,” he said.

“It’s well known that Clark Gable had terrible breath.” The silver-screen heartthrob wore dentures.

Katz swished with his patented mouthwash to erase the onion fumes. Seconds later, his breath reading was down to a kissable 114.

His fresh-breath crusade has earned him far more kudos than his regular dental practice ever did, Katz said. “You could do the best root canal in the world, no one’s going to thank you.